1. Field of the Invention
The invention generally relates to a method and an apparatus for image processing, in particular, to a method and an apparatus for motion compensated noise reduction (MCNR).
2. Description of Related Art
Motion compensation is an algorithmic technique used to predict a frame in a video, given the previous and/or future frames by accounting for motion of the camera and/or objects in the video. Motion compensation describes a picture in terms of the transformation of a reference picture to the current picture. The reference picture may be previous in time or even from the future. The motion vectors describe the transformation from one frame to another frame. The motion vector relates to the whole frame (global motion estimation) or specific parts thereof, such as rectangular blocks, arbitrary shaped patches or even per pixel. Furthermore, applying the motion vectors to a frame to synthesize the transformation to another frame is called motion compensation. The combination of motion estimation and motion compensation is a commonly used technology in image processing. After motion compensation, noise reduction may be necessary for better image quality. A conventional MCNR, which is motion compensation noise reduction, highly depends on the accuracy of motion compensation results because the goal of MCNR is to obtain the perfect matching patch by true motion given from motion estimation.
In addition, a block matching algorithm involves dividing the current frame of a video into macroblocks and comparing each of the macroblocks with a corresponding block and its adjacent neighbors in a nearby frame of the video (sometimes just the previous one). A vector is created that models the movement of a macroblock from one location to another. This movement, calculated for all the macroblocks comprising a frame, constitutes the motion estimated in a frame. A conventional block matching algorithm is easily affected by the result of full search, and the block matching algorithm has no mechanism to select the perfect similar patch since the block matching algorithm cannot determine whether selected patches are perfect matching.